Betulinic acid and its derivatives have been extensively studied in the past for their anti-tumor effects, but relatively little is known about its precursor betulin. In this study we showed that betulin, an abundant natural product, significantly inhibits the cell growth of human hepatoma HepG2 cells in a dose-dependent manner. In the presence of 10 μg/mL betulin, HepG2 cells undergo an apoptosis, as evidenced by apoptotic morphology such as cell shrinkage, membrane blebbing, nuclear condensation and fragmentation, apoptotic body formation, and caspase activation. Kinetics analysis shows that the depolarization of the mitochondrial membrane potential and the release of the mito- chondrial apoptotic protein cytochrome c occurred as early as 2 h post treatment of HepG2 cells with 10 μg/mL betulin. Proteolytic activation of caspase-9, but not caspase-8, was observed in this apoptosis process. Moreover, the inactivation of caspase-9 by its specific siRNA dramatically reduced betulin-induced caspase-3 activation and apoptosis. Taken together, our observations indicate that the activation of caspase-9 is critical for betulin-induced apoptosis of human hepatoma HepG2 cells.
LI YangSHEN Jared TaiyiGAO ChangLI QingJIN Ying-hua
In this study, we synthesized a series of 3-triazolo-coumarins and evaluated their antioxidant activities respectively by two methods： trapping 2,2＇-azinobis（3-ethylbenzothiazoline-6-sulfonate） cationic radical（ABTS＋＋） and oxidation of DNA which was induced by Cu2＋/glutathione（GSH）, ·OH and 2,2＇-azobis（2-amidinopropane hydrochloride）（AAPH）. Among the nine 3-triazolo-coumarins, compounds 6c and 6f-6i were synthesized for the first time, which exhibited the capability of terminating radical propagation-chains in oxidation of DNA induced by AAPH. In this study, we found that phenethylamine moiety, hydroxyl and ortho-methoxy are the key groups to en- hance the antioxidant activities of compounds.
LIU ZhihuiWANG YingnanSUN JingboYANG YangLIU QingwenLIU ZaiqunSONG Zhiguang
